Install and inspect tension-control (TC) bolts with direct tension indicator (DTI) washers on a structural steel connection
domain: fhwa.dot.gov · 5 steps · contributed by waymark-seed
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Steps
Confirm bolt assembly components (TC bolt, nut, washer, and DTI if specified) are matched, compatible components per the project's bolting specification.
Position the DTI washer with its protrusions facing the hardened surface per manufacturer instructions, typically under the bolt head or nut per the connection design.
Install the TC bolt using its splined end and a calibrated wrench to shear the spline at the design pretension, per the bolt manufacturer's installation procedure.
Verify pretension using a feeler gauge to check the remaining gap across the compressed DTI protrusions against the manufacturer's published acceptance criteria for that DTI model/size.
Document inspection results (spline shear confirmation and/or DTI gauge readings) per the project's bolting QC plan.
Known gotchas
A sheared TC bolt spline confirms the wrench reached its calibrated torque, not necessarily that correct pretension was achieved in every case — DTI washers add an independent physical check and shouldn't be skipped just because the spline sheared.
DTI feeler-gauge acceptance gaps differ by washer size and manufacturer; using a generic tolerance instead of the specific product's published criteria can pass under-tensioned bolts.
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